The present invention concerns a corner joint, a method for making such a corner joint and a corner piece to realise such a corner joint in view of a significative inertia reduction of the side members used for making frames.
In particular, it concerns a corner joint for cabinetwork which is made of hollow side members, whereby this corner joint has at least one insert corner piece with two insert parts extending at an angle which extend in the respective far ends of the side members to be joined.
In the first place, the invention is meant for making a corner joint with metal side members, but in a more general way it can also be used, at least to a certain extent, for making corner joints with side members made of other materials, such as PVC and such.
It is known that corner joints in frames, for example of windows and doors, which are made of hollow side members can be realised by mitre-joining the side members and by connecting them by means of a corner piece. It is also known that such a corner piece can be locked in different mechanical ways in relation to the side members, such as by means of inwardly bent wall parts meshing in recesses in the corner piece, by means of pins or by means of rotating eccentric pivots, etc.
What is important is that the mitres which are obtained in the end are sufficiently rigid, so that when the glass is put in, and also as time passes, the frame as a whole will not hang askew and the side members will not bend, as a result of which the frame would bulge.
It should be noted that up to now, the locking means are only used as locks with the above-mentioned techniques, without actually contributing to the rigidity and prestress of the obtained mitre as a whole. According to the present state of the art, the rigidity is mainly obtained thanks to the rigidity of the material of the corner joining piece in the corner itself. According to a critical, persistent misconception, it is often thought that such rigidity can be obtained by wedging up in a suitable manner, also called fastening by wedges.
The known techniques are disadvantageous in that fatigue in the corner joining piece soon becomes evident in the frame hanging askew and in that the slightest setting occurring after the wedging up also results in a bending of the side members.